Speed responsive switch

ABSTRACT

A speed responsive switch assembly comprising a housing adapted to be mounted between a conventional speedometer and cable, a first torque transfer member mounted in the housing for rotation by the cable, a second torque transfer member rotatably mounted in the housing and adapted to be connected to the speedometer, the first and second torque transfer members being coupled together through a plurality of motion transfer services angularly offset from the axis of rotation, such that an increase in speed produces longitudinal displacement of the first torque transfer member to effect switching. The assembly is also provided with adjustable compression spring for biasing the first torque transfer member axially toward the second, adjustment of the spring effecting the speed at which switching occurs.

United States-Patent n91 Brady I [11] 3,740,505 1 June 19,1973

1 SPEED RESPONSIVE SWITCH [76] Inventor: Clifford ll. Brady, 329 l-lillcrest,

R.F.D. No. 4, Sulphur Springs, Tex. 75482 22 Filed: Feb. 3, 1972 21 Appl. No.: 223,196

ZOO/61.46, 61.48, 61.53, 61.76, 80 R, 153 L,

153 LA, 16 B, 16 E, DIG. 32; 116/116 [56] References Cited 8 'UNl'IEDjSTATES PATENTS 1,860,972 5/1932 Wulfl'torst 200/16 B X 2,836,667 5/1958 Barden et al 3,047,683 7/1962 Shlesinger, .lr., 200/16 B X 3,021 ,402 2/ 1962 La Warre et al. ..200/6 1 .46 3,050,598 8/1962 Fennessey...... ..200/6 1 .46

Primary Examiner-J. R. Scott Attorney-Harvey B. Jacobson 57 8 ABSTRACT A speed responsive switch assembly comprising a housing adapted to be mounted between a conventional speedometer and cable, a first torque transfer member mounted in the housing for rotation by the cable, a second torque transfer member rotatably mounted in the housing and adapted to be connected to the speedometer, the first and second torque transfer members being coupled together through a plurality of motion transfer services angularly offset from the axis of rotation, such that an increase in speed produces longitudinal displacement of the first torque transfer member to effect switching. The assembly is also provided with adjustable compression spring for biasing the first torque transfer member axially toward the second, adjustment of the spring effecting the speed at which switching occurs.

14 Claims, 5 Drawing Figures l n H L! Patented June 19, 1973 2 Sheets-Sheet 2 SPEED RESPONSIVE SWITCH The present invention is generally related to speed responsive switches and, more particularly, to an improved speed responsive switch assembly adapted to be inserted between a conventional speedometer and its associated cable assembly to provide switching at a preselected speed.

a large number of moving parts and were relatively expensive to manufacture and install. Furthermore, many of these conventional switches were preset at the factory for tripping at a preselected speed, making it impossible or impractical to make adjustments after installation in order 'to provide a different speed setting 7 or to compensate for normal wear after long periods of use.

It is an object of the present invention to provide an improved speed responsive switch assembly for use with most conventional vehicles speedometer mechanisms to warn trailing drivers of the vehicles speed and which is comprised of a relatively small number of moving parts, is easily adjusted, and is economical to manufacture and install.

Another object of the present invention is to provide a unique speed responsiveswitch assembly including a pair of torque transfer members drivingly connected to each other by way of surfaces angularly offset from the axis of rotation to produce axial movement between the members-asa function of angular speed to effect switching at a preselected vehicle speed.

IT is a further object of the present invention to provide a versatile speed I responsive switch assembly including a pairof'rota'table torque transfer members which are axially displaced from each other against an present invention is generally indicated by the numeral 10 and includes a generally cylindrical elongated housing 12 threaded at one end thereof to a conventional speedometer instrument 14 and at the opposite end adjustment spring in order to effect switching as a function of preselected vehicle speed conditions.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as'more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:'

FIG. 1 is a perspective view of the switch assembly of the present invention mounted in a typical speedometer installation.

FIGL'2 is a sectional view taken along section 2-2 of drawings, the speed responsive switch assembly of the thereof to a speedometer cable assembly 16. A pair of electrical terminals 18 and 20 are adapted to accommodate electrical leads 22 which are connected to a warning circuit, such as that illustrated in FIG. 5. The switch assembly is provided with an adjustment screw 24 by which the speed to which the assembly responds may be preselected. Preferably, an electrical circuit is completed between terminals 18 and 20 when the associated vehicle reaches a predetermined low speed condition. Forexample, the switch assembly may be adjusted to respond to speeds of 20 miles per hour, or slower, thus, slow-down of the vehicle on a high-speed throughway or the like to a speed of 20 miles per hour would be effective to energize the warning circuit to flash warning lights to the drivers of trailing vehicles who normally would be driving at higher speeds. Upon returning the vehicle to a speed greater than the preselected speed, the warning circuit is automatically deenergized and the associated warning lights returned to their normal condition.

Referring now to FIGS. 2-4, the structure and opera 5 tion of the switch assembly may be seen in more detail. PReferably housing 12 is made of plastic, melamine, or other non-conductive materials and is provided with an axial bore extending between male and female threaded end portions 26 and 28, respectively. A pair of torque transfer members 30 and 32 are rotatably mounted in the bore of housing 12 and are provided with axially extending shaft portions 34 and 36 driv-.

spring- 48 applies pressure againstshoulder portion 48' to torque transfer member 32 by way of a teflon washer 50, or similar low friction bearing. The spring applies a mild force biasing torque transfer member 32 toward the left as shown in the drawings.

It will be appreciated that the torque transfer members are drivingly connected to each other by way of a plurality of motion transfer surfaces 52 which are angularly offset from the axis of rotation. The surfaces-of each torque transfer member are angularly' offset in a direction opposite to the adjacent surfaces. Thus, the combined surfaces define a plurality of angular teeth to provide serrated end portions to each torque transfer member.

Of course, the purpose of the switch assembly of the present invention is to provide switching as a function of the vehicle speed. This is achieved by effecting axial displacement of torque transfer member 32 by way of motion transfer surfaces 52. Most conventional speedometer instruments include an indication needle which is displaced through an angle against a spiral spring, or the like. Thus, as the speed of the vehicle increases, the force required to maintain the indication needle at the proper position also increases. GEnerally, this force is provided by way of a rotating magnet assembly. The rotating magnet and indication needle provide a load which is driven by the speedometer cable. As the speed increases, the torque load becomes larger. Thus, by inserting the switch assembly of the present invention between the speedometer and cable assembly, motion transfer surfaces 52 are subjected to the torque necessary to operate the speedometer instrument. While the torque is not necessarily a linear function of the speed, it will be appreciated that for each speed there is a corresponding torque transmitted to the speedometer instrument. Since the motion transfer surfaces 52 are angularly offsetfrom the axis of rotation, the greater the torque being transferred, the larger is the axial force acting upon torque transfer member 32 against coil spring 48.

The operation of the switch assembly may be explained as follows. Assuming that the vehicle is at rest and that the speedometer cable is not being rotated, the

torque transfer members will be in a position illustrated in FIG. 2, such that contacts 44 and 46 are abridged by ring 42. As the vehicle speeds up, the'torque load also increases and influences torque transfer member 32 to theright and, at a preselected speed, breaks the connection between contacts 44 and 46, as illustrated in FIG. .3. If the vehicle is-slowed down to the preselected low .speed, torque transfer member 32 will automatically move to the left to bridge contacts 44 and 46. It will be appreciated that shaft portion 36 associated with torque transfer member 32 is provided with an internal keyway 54 which slidably receives fitting 40 asswitch constructions have required presetting at the factory and did not include means permitting adjustment of the switching speed after installation. The switch assembly of the present invention is provided with an annular spring retaining collar 56 which is slidably mounted in the bore of housing 12 and is provided with an axial opening through which shaft portion 36 of torque transfer member 32 passes. Collar 56 bears against compression spring 48 by way of a teflon washer 58, or similar low friction bearing,'at one end. The opposite end of the collar is provided with a frustoconical surface 60 which is engaged by adjustment screw 24. It will be appreciated that the compression of coil spring 48 maybe increased by threading screw 24 in toward the frusto-conical' surface. Similarly, the spring compression may be reduced by turning screw 24 away from the frusto-conical surface, thereby allowing movement of collar 56 to the right.

Referring to FIG. 5, operation of the switch assembly of the present invention with a typical warning system may be more fully appreciated. Terminals 18 and 20 are connected in the circuit to energize a warning lamp 62, preferably, mounted at the rear of the associated vehicle. The warning lamp is connected to ground at 64 with the opposite side of its filament being connected to terminal 18 and the contact associated with a conventional brake switch indicated at 66. A source of voltage is provided through a battery 68, the positive side of which is connected to brake switch 66 through an ignition switch 70. Thus, under normal operating conditions, warning light 62 is energized by the battery light 62 will be energized through line 76, terminals 18- and 20, switch 74, and flasher unit 72.

From the foregoing description, it will be appreciated that the speed responsive switch assembly of the present invention is of relatively simple construction, easy to install with existing speedometer instruments, and is economical to manufacture. Furthermore, the switch assembly includes means permitting adjustment of the speed at which switch closure is effected and compensation for wear of the component pieces as a result of use over a long period of time. It should be noted that it is not intended that the assembly be limited to the exact number and configuration of the angular motion transfer surfaces illustrated or the position of the contact ring. Also, the switch assembly may be modified to provide switching at high speeds, if desired.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to .those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

What is claimed as new is as follows:

1. A speed responsive switch assembly adapted to be connected between a speedometer and associated cable for transmitting rotation therebetween, said assembly comprising a housing, a pair of substantially coaxially rotatable torque transfer members mounted in said housing and adapted to be drivingly connected to the cable and speedometer, respectively, said torque transfer members being axially disposed with respect to each other, one of said torque transfer members being provided with at least one cam surface at an angle to the axis of rotation, the other of said torque transfer members being provided with at least one cam follower surface engaging said cam surface to effect axial displacement therebetween, biasing means yieldingly urging said cam and follower surfaces of said torque transfer members toward each other, and switch means associated with said housing for completing a circuit upon displacement of one of said torque transfer members to a predetermined position relative to said housing.

2. The assembly set forth in claim 1 wherein said switch means includes a conductive member carried said other torque transfer member and a pair of contacts carried by said housing engaging said conductive member when said other torque transfer member is in said predetermined position.

3. The assembly set forth in claim 1 wherein said biasing means includes a coil spring and an annular spring seat member with an axial opening therein, said other torque transfer member having an axial portion extending through said opening and a shoulder portion, one end of said coil spring pressing against said shoulder portion and the opposite end pressing against said annular seat member.

housing to adjust the compression of said coil spring.

5. The assembly set forth in claim 4.wherein said annular seat member includes a frusto-conical surface and said housing is provided with an adjustment screw in engagement with said frusto-conical surface to adjust the axial position of said annular seat member, thereby setting the speed at which said other torque transfer member is influenced to said predetermined position.

6. The assembly set forth in claim 1 wherein said torque transfer member includes a continuous plurality of cam surfaces extending therearound with every other one being at an opposite angle to the axis of rotation as the adjacent cam surfaces.

7. The assembly set forth in claim 6 wherein said other torque transfer memberincludes a plurality of cam follower surfaces in sliding engagement with said cam surfaces.

- 8. A condition responsive switch comprising an elongated generally cylindrical hollow housing, first and tion transfer surfaces, biasing means for yieldingly.

urging said torque transfer members axially toward each other, and switch means associated with said housing for sensing axial displacement of one of said torque transfer members to a predetermined axial position.

9. The assembly set forth in claim 6 wherein said first torque transfer member includes a generally cylindrical portion with a torque transfer surface at one end thereof and a shaft portion at the opposite end thereof being adapted to be connected to a rotating drive cable. 7

10. The assembly set forth in claim 9 wherein said switch means includes a conductive ring member attached to the outer circumferential surface of said cylindrical portion and brush contact means carried by said housing in conductive engagement with said ring member when said first torque transfer member is axi-v ally displaced to said predetermined position.

11. The assembly set forth in claim 10 wherein said biasing means includes avcoil spring yieldingly urging said first torque transfer member toward said second torque transfer member.

12. The assembly set forth in claim 11 wherein said shaft portion of said first torque transfer member includes an elongated keywayadapted to slidably receive the endconnection of a drive cable.

13. The assembly set forth in claim 9 wherein said second torque transfer member includes a generally cylindrical portion with said motion transfer surfaces located at one end thereof and a. shaft portion extending axially from the opposite end thereof, adapted to be connected to angular speed responsive instrument.

14. The assembly set forth in claim 13 wherein said motion transfer surfaces extend continuously around said torque transfer members to define serrated-like end portions on said torque transfer members. 

1. A speed responsive switch assembly adapted to be connected between a speedometer and associated cable for transmitting rotation therebetween, said assembly comprising a housing, a pair of substantially co-axially rotatable torque transfer members mounted in said housing and adapted to be drivingly connected to the cable and speedometer, respectively, said torque transfer members being axially disposed with respect to each other, one of said torque transfer members being provided with at least one cam surface at an angle to the axis of rotation, the other of said torque transfer members being provided with at least one cam follower surface engaging said cam surface to effect axial displacement therebetween, biasing means yieldingly urging said cam and follower surfaces of said torque transfer members toward each other, and switch means associated with said housing for completing a circuit upon displacement of one of said torque transfer members to a predetermined position relative to said housing.
 2. The assembly set forth in claim 1 wherein said switch means includes a conductive member carried said other torque transfer member and a pair of contacts carried by said housing engaging said conductive member when said other torque transfer member is in said predetermined position.
 3. The assembly set forth in claim 1 wherein said biasing means includes a coil spring and an annular spring seat member with an axial opening therein, said other torque transfer member having an axial portion extending through said opening and a shoulder portion, one end of said coil spring pressing against said shoulder portion and the opposite end pressing against said annular seat member.
 4. The assembly set forth in claim 3 wherein said annular seat member is axially slidable relative to said housing to adjust the compression of said coil spring.
 5. The assembly set forth in claim 4 wherein said annular seat member includes a frusto-conical surface and said housing is provided with an adjustment screw in engagement with said frusto-conical surface to adjust the axial position of said annular seat member, thereby setting the speed at which said other torque transfer member is influenced to said predetermined position.
 6. The assembly set forth in claim 1 wherein said torque transfer member includes a continuous plurality of cam surfaces extending therearound with every other one being at an opposite angle to the axis of rotation as the adjacent cam surfaces.
 7. The assembly set forth in claim 6 wherein said other torque transfer member includes a plurality of cam follower surfaces in sliding engagement with said cam surfaces.
 8. A condition responsive swItch comprising an elongated generally cylindrical hollow housing, first and second torque transfer members co-axially rotatably mounted in said housing and being axially juxtapositioned, one of said torque transfer members being axially slidable in said housing, each of said torque transfer members being provided with a plurality of motion transfer surfaces, adjacent ones of which intersect each other and are oppositely angularly offset with respect to the axis of rotation, said torque transfer members slidably engaging each other along their respective motion transfer surfaces, biasing means for yieldingly urging said torque transfer members axially toward each other, and switch means associated with said housing for sensing axial displacement of one of said torque transfer members to a predetermined axial position.
 9. The assembly set forth in claim 6 wherein said first torque transfer member includes a generally cylindrical portion with a torque transfer surface at one end thereof and a shaft portion at the opposite end thereof being adapted to be connected to a rotating drive cable.
 10. The assembly set forth in claim 9 wherein said switch means includes a conductive ring member attached to the outer circumferential surface of said cylindrical portion and brush contact means carried by said housing in conductive engagement with said ring member when said first torque transfer member is axially displaced to said predetermined position.
 11. The assembly set forth in claim 10 wherein said biasing means includes a coil spring yieldingly urging said first torque transfer member toward said second torque transfer member.
 12. The assembly set forth in claim 11 wherein said shaft portion of said first torque transfer member includes an elongated keyway adapted to slidably receive the end connection of a drive cable.
 13. The assembly set forth in claim 9 wherein said second torque transfer member includes a generally cylindrical portion with said motion transfer surfaces located at one end thereof and a shaft portion extending axially from the opposite end thereof, adapted to be connected to angular speed responsive instrument.
 14. The assembly set forth in claim 13 wherein said motion transfer surfaces extend continuously around said torque transfer members to define serrated-like end portions on said torque transfer members. 